1. Field of the Invention
The present invention relates to a method, computer readable medium and apparatus for converting color image resolution, and more particularly relates to a method, computer readable medium and apparatus for converting a relatively low resolution color image having bi-level and multi-level pixel values into a relatively high resolution color image.
2. Discussion of the Background
In general, a digital image displayed on a monitor screen, such as an image of an Internet web page, has relatively low image resolution, for example, 72 dots per inch (dpi). On the other hand, recent color image printers can print images with a relatively high image resolution, such as 400 dpi, 600 dpi, 1200 dpi, etc., as compared to the above-noted digital image displayed on the monitor screen. In other words, a printed image can have more picture elements (pixels) per unit area than an image displayed on a monitor screen. Therefore, when image data displayed on a monitor screen is directly printed on a sheet of paper as a hardcopy by a color image printer, the size of the printed image becomes smaller than that on the monitor screen. To print a hardcopy with a preferable size by capitalizing on a high image resolution capability of color image printers, relatively low resolution image data is converted into relatively high resolution image data.
As another example, an image taken by a digital still camera, or scenes taken by a video camcorder, etc., may also have a low image resolution. Therefore, such images may also need to be converted into relatively high resolution images. In this way, an image printer can print the image substantially in a full paper size. A whole image on a monitor screen generally includes various categories of images, such as text and character strings, text and character strings having shadows, text and character strings processed by a so-called anti-aliasing processing, photographs, illustrations, drawings, etc. Images are also categorized into bi-level data images, such as ordinary text strings and multi-level data images, such as continuous toned photographs.
As described in several Japanese Laid-Open Publications, various methods and devices convert a relatively low resolution image into a relatively high resolution image according to a respective image category. However, the discloses methods and devices do not adequately address converting an image resolution of an image comprising various types of image categories, while reducing jagged images, improper coloring, blurring and doing so with a relatively short execution time for the image conversion.